Group A Streptococcal diseases: For health professionals

What health professionals need to know about Group A streptococcal diseases

Group A streptococcus (GAS) bacteria, Streptococcus pyogenes, are Gram-positive beta-hemolytic bacteria of which over 240 emm types (genotypes) have been identified.

GAS can be present on the skin and throat, as well as in the vagina or perianal area of asymptomatic carriers. It can also cause a range of clinical presentations in the form of non-invasive and invasive disease.

Infections typically peak during the winter and early spring and decrease over the summer.

Clinical manifestations

Common presentations of GAS include:

pharyngitis
skin infection such as impetigo, erysipelas, cellulitis
scarlet fever

Occasionally, GAS causes invasive infections, which can be severe and possibly life threatening. This occurs when GAS infects deep tissues and organs that are usually sterile. This can result in serious conditions, such as:

septicemia
necrotizing fasciitis (flesh eating disease)
pneumonia
Streptococcal Toxic Shock Syndrome
septic arthritis
meningitis
puerperal sepsis

Treatment

Antibiotics are used to treat both non-invasive and invasive GAS infections. iGAS cases must be reported to local public health, as close contacts may be eligible for post-exposure prophylaxis. More information on the management of iGAS can be found in the guidelines for the Prevention and Control of Invasive Group A Streptococcal Disease.

Risk factors

Multiple studies have highlighted that the risk of invasive GAS disease is significantly associated with:

open wounds or breaks in the skin (e.g. cuts, burns, sores, varicella or shingles)
chronic diseases (e.g. diabetes, pulmonary, hepatic or cardiac disease)
weakened immune system (immunosuppression) either from:

disease (HIV/AIDS)
cancer treatments (radiation, chemotherapy)
taking anti-rejection drugs following an organ or bone-marrow transplant

living in a crowded environment (e.g. dormitories, shelters, army barracks)
recent infection with chickenpox or with respiratory viruses such as influenza
substance use, including use of injectable drugs
recent close contact with someone with a GAS or iGAS infection
during childbirth and in the post-partum period

Invasive GAS occurs more often in young children under 5 years of age and adults aged 65 years of age and older.

Surveillance

The Public Health Agency of Canada (PHAC) conducts annual national routine iGAS surveillance. This is done through the Canadian Notifiable Disease Surveillance System. iGAS has been nationally notifiable since January 2000.

Basic demographic information is available, such as:

sex
age group
province or territory

Non-invasive GAS (i.e., strep throat, scarlet fever) is not reported nationally.

The National Microbiology Laboratory (NML) conducts laboratory-based surveillance of the bacteria that causes invasive GAS. Data are collected by the NML when provinces and territories send iGAS isolates for laboratory testing and emm sequencing. Laboratory data is an important source to monitor current trends in iGAS.

For more information:

Number of invasive Group A streptococcal disease cases in Canada

Since the early 2000s, the incidence rate of iGAS has increased steadily, with the exception of 2020 and 2021, where incidence rates decreased during the COVID-19 pandemic.

The rate has doubled from 2.7 cases per 100,000 people in 2001 to 5.6 cases per 100,000 people in 2021. Figure 1 shows the number of cases and incidence rates of iGAS in Canada by year from 2000 to 2021.

Figure 1. Text version below. — **Figure 1. Number of invasive Group A streptococcus cases in Canada**

Figure 1. Number of invasive Group A streptococcus cases in Canada
Year	Cases	Incidence
2000	863	2.81
2001	830	2.68
2002	866	2.76
2003	1,039	3.28
2004	857	2.68
2005	1,025	3.18
2006	1,194	3.67
2007	1,419	4.31
2008	1,469	4.42
2009	1,354	4.03
2010	1,410	4.15
2011	1,643	4.78
2012	1,618	4.66
2013	1,665	4.75
2014	1,831	5.17
2015	1,894	5.3
2016	2,168	6
2017	2,492	6.82
2018	3,190	8.61
2019	3,095	8.23
2020	2,603	6.85
2021	2,127	5.56

Figure 2. Text version below. — **Figure 2. Age-group specific incidence rates of invasive Group A Streptococcal Disease in Canada**

Figure 2. Age-group specific incidence rates of invasive Group A Streptococcal Disease in Canada
Year	< 1	1-4	5-9	10-14	15-19	20-24	25-29	30-39	40-59	60 +
2000	5.61	3.99	2.95	1.12	0.76	0.82	2.94	3.14	1.97	5.56
2001	4.87	3.58	2.23	0.87	1.18	1.09	2.12	3.12	1.98	5.34
2002	6.4	3.3	2.01	1.09	0.94	1.4	2.01	2.68	2.44	5.41
2003	6.66	4.65	2.77	1.59	1.03	1.42	1.57	3.91	2.8	6.11
2004	7.4	3.58	2.2	0.98	1.03	1.45	2.68	3.15	2.23	4.48
2005	6.49	2.99	3	1.13	0.97	0.98	2.93	4.13	3.04	5.12
2006	6.38	3.83	3.18	1.1	0.9	2.04	2.84	5.1	3.5	5.67
2007	8.33	3.8	3.11	1.31	1.3	1.77	3.33	6.21	4.31	6.57
2008	6.71	4.43	2.74	1.33	1.51	2.87	3.34	5.5	4.66	6.57
2009	9.53	3.65	2.68	1.65	1.24	1.66	3.27	4.46	4.04	6.61
2010	8.47	4.08	3.85	1.38	1.2	1.89	2.59	4.51	4.04	7
2011	9.83	5.78	4.31	2.29	1.97	2.21	2.53	5.24	4.7	7.45
2012	9	4.87	2.92	1.48	1.37	2.26	2.98	4.91	4.97	7.42
2013	9.72	4.6	3.28	2.01	1.02	2.19	3.3	5.27	5.06	7.19
2014	9.18	5.24	3.62	1.37	1.27	2.48	3.69	5.29	5.05	8.72
2015	13.87	4.4	3.6	1.06	1.53	2.71	3.99	5.57	5.39	8.36
2016	7.31	6.41	3.64	1.77	1.34	2.81	5.07	7.53	6.17	8.7
2017	8.71	6.21	3.12	1.74	1.77	3.54	5.05	8.33	7.83	9.48
2018	10.63	6.58	4.38	2.31	2.23	3.94	6.95	9.33	9.89	12.69
2019	8.87	6.47	4.07	1.13	1.8	3.68	6.93	9.39	9.59	11.95
2020	7.57	3.68	1.71	0.68	1.81	3.71	5.71	8.7	9.35	8.35
2021	7.77	1.9	0.64	0.67	0.87	2.9	3.72	7.17	8.38	6.44

Based on Canadian data, the age groups most affected are infants under 1 year of age and adults between 40 to 59 years of age and those 65 years of age and older. The 10-year average (2011-2021) age group-specific incidence rates for those age groups were:

9.31 cases per 100,000 for infants under 1 year of age
8.79 cases per 100,000 in adults 65 years of age and older
6.94 cases per 100,000 for adults between 40 to 59 years of age

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Date modified:: 2024-02-13

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